These are the commercial jet engines you see, like the Boeing 777, 747, Airbus A330 and A380s. Though there is a considerable reduction of the engine thrust, at these altitudes the lower drag associated with low air density means a more economical flight with a higher True Air Speed.
Crepitus in the knees may be caused by knee injuries such as meniscus tears. These are fairly common in people who play sports, jog, or run. A meniscus tear can cause crepitus as the joint moves. Chondromalacia patella is a dull ache behind the kneecap, usually caused by overuse or injury. There will be damage to the undersurface cartilage covering the kneecap.
Causes of Housemaids knee. Acute prepatellar bursitis can be caused by a direct blow or fall on the knee. This ruptures blood vessels which bleed into the bursa causing swelling and triggering an inflammation reaction in the walls of the bursa.ymptoms of Housemaids knee include pain and tenderness at the front of the kneecap and just below it. The kneecap or patella may be swollen and warm to the touch.